Various substances have been known as agents for enhancing the strength of cement cured products, such as mortar and concrete, in which portland cement, mixed cement, etc., has been used. For example, French Patent Application No. FR2485949A1 described the use of tetrahydroxylethylethylene diamine (referred to hereinafter as “THEED”) and other similar derivatives of ethylene diamine as cement grinding aids. Grinding efficiency and strength (especially at 28 days) were taught to be better with these materials than with triethanolamine (referred to hereinafter as “TEA”). Also disclosed were reaction products with acetic acid and butylphosphoric acids.
U.S. Pat. No. 4,401,472 disclosed the use of poly(hydroxyalkylated) polyethyleneamine, poly(hydroxyethyl)polyethyleneimine, or mixtures of these used as additives in a cement mix that could include hydraulic cement, aggregate, and water. These additives were deemed to function as strength enhancers for the cementitious mix.
U.S. Pat. No. 5,084,103 disclosed triisopropanolamine and other trialkanolamines used as strength enhancing additives for later age strength (7–28 days). These additives could be admixed with cement powder or interground as a grinding aid during finish milling of the cement clinker.
U.S. Pat. No. 6,290,772 disclosed the use of hydroxylamines including N,N-bis(2-hydroxyethyl)-2-propanolamine and N,N-bis(2-hydroxypropyl)-N-(hydroxyethyl)amine, to enhance the compressive strength of the cement compositions after 1, 3, 7, and 28 days. Also disclosed was a mixture involving other hydroxylamines such as triethanolamine. The patent further taught that these amines could be added as grinding aids in the manufacture of cement.